What he said above and Dna rna all that chapter too genetics !! And I dunno if you've done the plant yet or stuff but they could tend to do that at the end and the fact none came up this year I'd learn it well because at the end you could get bored and not bother learning it as u can leave it out but then it could leave u short in a q14 or q15 when you might have a full 30 marks right on one part
The best way to prepare if studying on your own is to combine your study with the use of the exam papers and get used to how topics are asked. Test yourself against past paper questions and then use the marking schemes to assess how well you are doing. The past papers and marking schemes are available on examinations.ie under the archived material section.